Fix an issue where toolhead can crash on repeat homing because safe_z is being blindly overwritten with current z position

[jmeier5261]

Address an issue with blindly assuming that if Z is already homed then it is above safe_z which was overwriting the value of safe_z to the current Z position when re-homing if Z was already homed, regardless of whether the current position was actually above the safe_z. Additionally included small typo fixes for logs.

Use case here is that because the machine is in a homed state, if my print fails or ends or any other action leaves my toolhead below specified safe_z height, the machine will not be returned to the actual safe_z when re homing because the code added in ac98aefb41dad7a62af7ded3610c21b70bca1efb will overwrite the user variable safe_z with whatever the current Z position is. Ideally we would want to do this only if the current Z is actually above configured safe_z